Ferrite-loaded cavity beam-shifting antenna



1962 E. w SEELEY ETAL 3,069,680

FERRITE-LOADED CAVITY BEAM-SHIFTING ANTENNA Filed July 26, 1960 2Sheets-Sheet l MICROWAVE I4 LOAD END FIG. 3

ELWIN W. SEELEY DOUGLAS M. MONCRIEFF INVENTORS By jxm ATTORNEYS Dec. 18,1962 E. w. SEELEY ET AL 3,069,680

FERRITE-LOADED CAVITY BEAM-SHIFTING ANTENNA Filed July 26, 1960 2Sheets-Sheet 2 HIHIIIIHIIHHHHIHIIIHIIIHIIHH ELWIN W. SEELEY DOUGLAS M.MONCRIEFF INVENTORS ATTORNEYS 3,%9,68fi Patented Dec. 18, 1962 Theinvention herein described may be manufactured and used by or for theGovernment of the United States of America for governmental purposeswithout the payment of any royalties thereon or therefor.

The present invention is related to beam-shifting antennas and moreparticularly to a simple lightweight and extremely compact multi-slotwaveguide antenna.

Heretofore, beam shifting was produced by mechanical systems, or by asystem of manifolding to distribute microwave energy to individualwaveguide elements, where each element contained a phase shifterfollowed by a radiator. In the manifolded system beam shifting isaccomplished by applying electric currents to the phase shifters.However, the mechanical method of beam shifting is slow and readilysubject to wear and malfunction. Also, the manifolded method of beamshifting requires a considerable amount of space to accomplish powerdistribution and each consecutive phase shifter must shift a greateramount to maintain proper beam proportion since phase shift is notaccumulative or reciprocal.

The present invention overcomes the above mentioned disadvantages ofprevious beam shifting systems by using ferrite-loaded solenoid-woundcylindrical cavities coupled with a slot array waveguide. The use offerriteloaded phase shift cavities induces phase shift into a waveguidecontaining a slot array and causes the beam lean angle to change; thephase shift is varied by changing the electromagnetic current in thesolenoid coil around the cavity, thus changing the permeability of theferrite in the cavity, thereby producing phase shift by Faraday rotationof the high frequency energy as it travels into thru and back out of thecavity. In the present invention the phase shift is accumulative.

It is an object of the invention, therefore, to provide a novelmulti-slot beam shifting waveguide antenna that is extremely compact,lightweight and simple in construction.

It is also an object of the invention to provide a multislot waveguideantenna in which the beam may be electronically shifted at a very highrate without changing the frequency of the transmitter.

It is another object of the invention to provide a new beam shiftingantenna having solenoid phase shifting elements.

It is a further object of the invention to provide beam shifting in amulti-slot waveguide antenna by applying current to solenoids coupledtherewith. 7

Other objects and many of the attendant advantages of this inventionwill become readily appreciated as the same becomes better understood byreference to the following detailed description when considered inconnection with the accompanying drawings wherein:

FIGURE 1 is a perspective view of a preferred embodiment of theinvention;

FIGURE 2 is a planar view of the top side of the waveguide of FIGURE 1,with the solenoids removed, showing the coupling slots;

FIGURE 3 is a planar view of the bottom side of the waveguide of FIGURE1 showing an example of a slot array therein;

FIGURE 4 is a cross-sectional view of the waveguide antenna taken alongline 44 of FIGURE 1;

2 FIGURE 5 is a cross-sectional view of the waveguide antenna takenalong line 5-5 of FIGURE 1.

Referring now to the drawings, like numerals refer to like parts in eachof the figures of drawing.

A basically conventional waveguide section 10, as

- shown in FIGURE 1, having a conventional slot array consisting of aplurality of radiating slots 12 on the under side thereof, as shown inFIGURE 3, is provided with a plurality of small cylindrical cavities 14attached to the upper side thereof. The cylindrical cavities 14 are eachlocated electrically between radiating slots 12, along the longitudinalaxis of the waveguide, and physically on the opposite side of thewaveguide from the array of slots. Each cylindrical cavity is coupled tothe waveguide 10 by a pair of crossed slots 16, shown in FIGURE 2, and

has a solenoid winding 18 surrounding its cylindrical surface. Flange 19extends along one edge of the waveguide for partially supportingcavities 14.

Cylindrical cavities 14 are ferriate loaded and may be constructed, asshown in FIGURE 5, from a cylinder 20, of brass for example, having acircumferential flange at opposite ends thereof holding solenoid winding18 in place. A polystyrene sleeve 22 fits within cylinder 20 and aboutthe cylindrical sides of a poly foam support cup 24 which holds a smallferrite core 26. A cavity cap 28, of brass or the like, having a lowfrequency ferrite disc 29 recessed therein completely encloses the topof each cylindrical cavity 14. Lead wires 30 are used for feedingcurrent to the solenoids. Ferrite disc 29 has for its purpose to enhancethe DC. magnetic field or the static magnetic field of the solenoid 18.Cylindrical cavities 14 are located more nearly along one side of thewaveguide 10, as can best be seen from crosssectional views of FIGURES 4and 5.

As microwaves travel along waveguide 10 they will enter each cavity 14through a coupling cross slot 16, pass up through the ferrite core 26,be reflected by cavity cap 28 back through ferrite core 26, and coupleback to the waveguide by means of coupling slot 16 to proceed to thenext cavity. Application of electric current to the solenoids 18 willalter the electrical length of the cavities I4 and thus alter theelectrical spacing between antenna slots 12; this will produce beamshift. In other words the ferrite loaded cavities 14 inject phase delayinto the waveguide between the slots 12 of the slot array by effectivelychanging the electrical spacing between the slots through theapplication of current to the solenoids wound about the cavities. Theamount of phase delay can be varied by varying the amount of currentapplied to the solenoids IS. The size and shape of the ferrite core canalso be varied to produce the results desired.

Extreme compactness of the antenna of the present invention can beachieved because the basic dimensions of a slot array require littlealteration. The cavities 14 are, in effect, in series, producing adesired accumulated phase shift along the waveguide. Only a small amountof phase shift from each cavity is needed to produce a large amount ofbeam shifting in the array. Using the present system for phase shiftingpermits the beam of an antenna to sweep electronically and easily evenat very high rates.

Obviously many modifications and variations of the present invention arepossible in the light of the above teachings. It is therefore to beunderstood that within the scope of the appended claims the inventionmay be practiced otherwise than as specifically described.

What is claimed is:

l. A beam shifting antenna comprising a section of waveguide having aplurality of radiating slots in one side thereof, a plurality ofcoupling slots in the side of said waveguide opposite said radiatingslots and positioned electrically between said radiating slots along alength of said waveguide, a plurality of ferrite loaded cavities mountedon said section of waveguide and coupled thereto by means of saidcoupling slots, each of said ferrite loaded cavities consisting of ametal cylinder having a foam-plastic cup-shaped support thereinsupporting a ferrite core, a solenoid winding about each of said ferriteloaded cavities, said solenoid wound cavities being operable to vary theelectrical spacing between said radiating slots by applying varyingamounts of current to said solenoid winding whereby the application ofelectrical current to the solenoid windings alters the electrical lengthof the cavities and thus alters the electrical spacing between antennaslots to produce beam shift, and wherein a small amount of phase shiftfrom each cavity produces atlarge amount of beam shifting in theantenna.

2., A beam shifting antenna comprising a section of waveguide having aplurality of radiating slots in one side thereof, a plurality ofcoupling slots in the side of said waveguide opposite said radiatingslots and positioned electrically between said radiating slots along alength of said waveguide, a plurality of ferrite loaded cavities mountedon said section of waveguide and coupled thereto by means of saidcoupling slots, each-of said ferrite loaded cavities consistingof ametal cylinder hav ing a foam-plastic cup-shaped support thereinsupporting a ferrite core and having a metal cap enclosing the end ofeach saidcylinder at the open end of said plastic cup, said metal capcontaining a disc of ferrite for enhancing the magnetic field of thesolenoid, a solenoid winding about each of said ferrite loaded cavities,said solenoid wound cavities being operable to vary the electricalspacing between said radiating slots by applying varying amounts ofcurrent to said solenoid winding whereby the application of electricalcurrent to the solenoid windings alters the electrical length of thecavities and thus alters the electrical spacing between antenna slots toproduce beam shift, and wherein a small amount of phase shift from eachcavity produces a large amount of beam shifting in the antenna.

References Cited in the file of this patent UNITED STATES PATENTS2,905,940 Spencer et al. Sept. 22, 1959 2,946,056 Shanks July 19, 19602,96lg658 Spencer et al Nov. 22, 1960 3,032,762 Kerr May 1, 1962

1. A BEAM SHIFTING ANTENNA COMPRISING A SECTION OF WAVEGUIDE HAVING APLURALITY OF RADIATING SLOTS IN ONE SIDE THEREOF, A PLURALITY OFCOUPLING SLOTS IN THE SIDE OF SAID WAVEGUIDE OPPOSITE SAID RADIATINGSLOTS AND POSITIONED ELECTRICALLY BETWEEN SAID RADIATING SLOTS ALONG ALENGTH OF SAID WAVEGUIDE, A PLURALITY OF FERRITE LOADED CAVITIES MOUNTEDON SAID SECTION OF WAVEGUIDE AND COUPLED THERETO BY MEANS OF SAIDCOUPLING SLOTS, EACH OF SAID FERRITE LOADED CAVITIES CONSISTING OF AMETAL CYLINDER HAVING A FOAM-PLASTIC CUP-SHAPED SUPPORT THEREINSUPPORTING A FERRITE CORE, A SOLENOID WINDING ABOUT EACH OF SAID FERRITELOADED CAVITIES, SAID SOLENOID WOUND CAVITIES BEING OPERABLE TO VARY THEELECTRICAL SPACING BETWEEN SAID RADIATING SLOTS BY APPLYING VARYINGAMOUNTS OF CUR-